At petroleum handling facilities such as refineries, storage facilities, terminal facilities, and gasoline stations, spillage of liquid hydrocarbons can result in the contamination of subsurface or surface ground water in the immediate vicinity. The problem of ground water contamination can occur as a result of slow leakage over time or as a more catastrophic spillage event. In either case, the liquid hydrocarbons can seep through the ground to the ground water table level or collect in open streams or ponds. Because liquid hydrocarbons have specific gravities that are less than water and are generally immiscible with water, liquid hydrocarbons often form a layer on top of the ground water table.
After a catastrophic spill, the liquid hydrocarbons tend to form an especially thick layer on top of the ground water table at the point directly below the spill. In order to exploit the fact that the liquid hydrocarbons are in a relatively concentrated area beneath the point of the spill, and before the liquid hydrocarbons have dispersed due to their own hydraulic head and general ground water flow, it is advantageous to make a well bore at the point of the spill and pump as much of the liquid hydrocarbon out of the well bore as soon as possible. Early removal of the concentrated liquid hydrocarbons reduces the hydraulic head of liquid hydrocarbons and helps minimize the lateral spreading of the contamination.
Normally where ground water clean-up is to be undertaken, it is necessary to acquire permits from environmental protection agencies before the decontaminated ground water can be discharged from the site. In most spillage cases where the public health and safety are not immediately affected, there may be administrative delays in acquiring such permits and until such permits are acquired, any water that is pumped to the surface must be stored or trucked away to an approved disposal treatment site until such time as the requisite permit to discharge the ground water has been acquired. It is therefore important, during the early phase of a clean up of a catastrophic spill, while the liquid hydrocarbons remain concentrated beneath the spill and when no discharge permit is avilable, to pump the minimum amount of ground water as a percentage of the liquid hydrocarbons to the surface. In order to exploit the situation, the intake of the pump must be located within the liquid hydrocarbon layer so that the smallest amount of ground water is pumped to the surface.
Skimming vessels which float in the liquid hydrocarbon layer have been used to collect the liquid hydrocarbon. A conduit, such as a coiled tube, connected to the skimming vessel, conducts the liquid hydrocarbon in the skimming vessel to the intake of a pump. Such pumps conventionally rely on the head created by the height of the liquid hydrocarbon to force the liquid hydrocarbon through the intake of the pump and fill the pump chamber. Accordingly, these conventional pumps were located below the skimming vessel and within the ground water. Because these conventional pumps must be positioned within the ground water, there is a risk of the ground water seeping into the liquid hydrocarbons as the liquid hydrocarbons are removed by the pump. There is the further risk of the liquid hydrocarbons in the well bore corroding the outer surface of the pump. In addition, these conventional pumps are normally too large for smaller diameter (2-4 inches) well bores. The smaller diameter wells are often preferred because they can be drilled more quickly and with less expense than larger diameter well bores.
In the prior art, a variety of pumps are known and are referred to as bladder pumps. Bladder pumps generally comprise a pump housing and a flexible bladder situated in the pump housing, separating the pump housing into an outer chamber and an inner chamber. These conventional bladder pumps rely on the pressure created by the height of a liquid to force liquid into the inner chamber. Air or hydraulic fluid is forced into the outer chamber to collapse the bladder and force the liquid out of the bladder pump. Accordingly, conventional bladder pumps must be positioned below the layer of liquid hydrocarbons and within the ground water when used in a well bore to pump liquid hydrocarbons to the surface. Again, because these bladder pumps must be positioned within the ground water, the liquid hydrocarbons often corrode the outer surface of the bladder pumps. Further, because the bladder pumps are located within the ground water and are connected by a flexible coiled tube to the skimming vessel above, the spring force of the coiled tube tends to pull the skimming vessel downward and below the water line. As a result, ground water can flow into the vessel and mix with the liquid hydrocarbons being pumped to the surface.
After a significant portion of liquid hydrocarbons are removed from the well bore, the layer of liquid hydrocarbons becomes thinner and further measures must be taken to remove the liquid hydrocarbons. It is necessary to pump large quantities of ground water and create a cone of depression within the well bore to remove the remaining liquid hydrocarbons. Conventionally, to create a cone of depression, a larger diameter (about 6 inches) well bore must be drilled and a submersible pump with a bottom intake is positioned within the ground water. The skimming vessel is placed near the center of the cone of depression to collect the remaining liquid hydrocarbons. These submersible bottom intake pumps are normally operated by compressed air or hydraulic fluid pressure. Accordingly, the well bore above the ground water level is occupied by an air or hydraulic fluid input line and a ground water output line. Therefore, there is very little space in the well bore for a separate pump to recover the liquid hydrocarbons gathered by the skimming vessel and the lines that normally accompany such a pump.
Another problem with conventional extraction systems wherein a cone of depression is created occurs when the submersible pump removes ground water from the well bore too rapidly and the level of liquid hydrocarbons drops to the point of intake of the submersible pump. The liquid hydrocarbons are then drawn through the intake of the submersible pump and pumped to the surface with the ground water. The ground water pumped to the surface is then contaminated by the liquid hydrocarbons and the liquid hydrocarbons must be removed from the ground water at surface. Storage of the contaminated ground water and removal of the liquid hydrocarbons from the contaminated ground water at the surface is very costly.
Therefore, there is a need for a relatively small pump which can fit into a 2-4 inch well bore and operate to pump liquid without being submersed therein. Also, there is a need for a pump which can withstand exposure to corrosive liquid hydrocarbons. Further, there is a need for an extraction pump system which removes a minimum of ground water with the liquid hydrocarbons. There is also a need for an extraction pump system which separately pumps ground water to create a cone of depression and which separately pumps liquid hydrocarbons.